And there's a firmware version for the OT1+ that reports one of the
external ADC inputs as an omni DF signal level. I sent it off to
someone who was going to try it out, haven't heard back yet. I've only
tested it myself with a variable power supply input.
Scott
N1VG
Stephen H. Smith wrote:
> Bob Bruninga wrote:
>>>> Yes, this is a kludge, using only existing hardware, and no special
>> firmware and no special software and not even APRS. THis is just a
>> simple way to do the original APRS [plan for automatic DFing networks
>> which we never could implement because only APRSdos had it built in
>> and without other players, it is one hand clapping.
>>>> But it is easy to see, that Opentrack, Tiger track or Byonics or
>> anyone that is making pic trackers could easily modify an input pin on
>> their devices so that not just the presence of the squelch on the
>> moiitor can be transmitted, but now also the SIGNAL STRENGTH. Doing
>> this, gives us the automatied DF signal strength network APRS was
>> originaly supposed to do...
>>>>>> While the TinyTrak and TigerTrack don't have an analog input for RSSI
> (Received Signal Strength Indication), the OpenTracker DOES have such an
> input now. Usually it's used for temperature or battery voltage
> reporting.
>>>> The real problem is trying to get a point in the radio receiver that
> varies with signal strength. On most FM rigs, the IF tends to saturate
> quite abruptly somewhere between half a microvolt or so and about 1-2
> microvolts (i.e. typical FM limiting effect - note how the S-meter on
> most FM rigs tend toward an "all-or-nothing" reading).
> I've struggled with this issue for over a decade now building setups for
> radio signal strength coverage mapping systems. I've wound up tapping
> the FM rig's IF somewhere before the limiting saturated stages, and
> routing it to an external spectrum analyzer or an HF-SSB rig turned to
> the FM rig's IF freq. The non-saturating IF of the SSB/AM rig
> provides a useful logarithmic S-meter response over a wide range of
> signal levels (at least 4 decades). My best measuring setup uses an
> IF-1500 service monitor. This unit has an FM receiver and an AM
> receiver driven off the same IF system. The receivers demodulate
> whatever is at the center of the spectrum analyzer display. The AM
> receiver drives a S meter with a useable more-or-less logarithmic
> response between 0 and full scale (yes, it's an analog meter!) of over
> 60 dB.
> I can tune the IFR's receiver to any freq between about .5 and 1000 MHz
> so I can tap the IF of just about anything. One could connect an
> antenna directly to the IFR RX-in, but it's not very sensitve, and it
> has NO front-end selectivity. The transceiver being tapped provides
> 10-20 dB gain and the selectivity of it's front-end and 1st IF filters
> which makes the IF VASTLY more usable for off-air monitoring.
>>>> --
>> Stephen H. Smith wa8lmf (at) aol.com
> EchoLink Node: 14400 [Think bottom of the 2M band]
> Home Page: http://wa8lmf.com --OR-- http://wa8lmf.net>> NEW! World Digipeater Map
>http://wa8lmf.net/APRSmaps>> JavAPRS Filter Port 14580 Guide
>http://wa8lmf.net/aprs/JAVaprsFilters.htm>> "APRS 101" Explanation of APRS Path Selection & Digipeating
>http://wa8lmf.net/DigiPaths>> Updated "Rev H" APRS http://wa8lmf.net/aprs> Symbols Set for UI-View,
> UIpoint and APRSplus:
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